AB0692 SERUM INTERFERON Α (IFNΑ) LEVELS AND SYSTEMIC LUPUS ERYTHEMATOSUS (SLE) DISEASE ACTIVITY IN SLE PATIENTS IN ESTONIA. A PROSPECTIVE COHORT STUDY OF 40 SLE PATIENTS IN ESTONIA
Authors: S. Meisalu, K. Kisand, L. Haljasmagi
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> SLE is a rare chronic autoimmune disease with polymorphic clinical manifestation. It has been found that the interferon signature is detectable in 80% of SLE patients. With the implementation of measuring IFNα levels, additional method to evaluate SLE has been provided. <h3>Objectives</h3> The aim of the present study is to characterize a sample of Estonian SLE patients. <h3>Methods</h3> Consecutive outpatient and inpatient patients with rheumatologist diagnosed SLE (≥20 years) were enrolled in East-Tallinn Central Hospital. Two study visits were done with 6 months apart to evaluate disease activity, current treatment, organ involvement, immunological findings and comorbidities. In addition, data from medical records were collected: organ involvement and immunological findings at the time of diagnosis and initial treatment. SLE disease activity was measured using SLEDAI 2K (Systemic Lupus Erythematosus Disease Activity Index 2K) score. Blood tests were taken to measure interferon levels using Simoa (Single Molecul Array) method. To evaluate the extent of the deviation of IFNα levels in patients with SLE compared to non-autoimmune individuals, age and gender matched control group was used. Interferon score was calculated according to interferon induced gene expression in blood cells collected to RNA stabilizing tubes. Spearman correlation was used for correlation analyses and chi-square and Fisher test for the group comparison. <h3>Results</h3> Among 40 patients (mean age 50 (standard deviation ±12.4) years, mean disease duration 12 (±9.9) years, mean SLEDAI 2K at diagnosis 10 (±3.9)) 92.5% were females. Mean SLEDAI 2K value at entering into the study was 4 (±3.4) similar to the value after six months 4 (±5.0). Median IFNα levels during first and second study visits were respectively 133 fg/ml (IQR=560) and 117 fg/ml (IQR=477). At first and second study visit respectively 48% and 45% of patients had low IFNα levels (&lt;100 fg/ml), 35% and 37% had high IFNα levels (100-1000 fg/ml) and 18% of patients had very high IFNα levels (&gt;1000 fg/ml). IFNα levels correlated poorly or not significantly in either time point with SLEDAI 2K (r=0.3280, p=0.04 and r=0.5460, p=0.0004), organ involvement (for joints r= 0.2352, p=0.14 and r=0.3433, p=0.03; for skin r=0.0216, p=0.89 and r=-0.0532, p=0.76), Rituximab treatment (r=0.2061, p=0.20 and r=0.3201, p=0.05). IFNα levels correlated strongly with IFN score (r=0.9325, p&lt;0.0005) and 78% of patients had elevated IFNa levels compared to 98 percentile of healthy controls (median IFNα level 0.5605 fg/ml, IQR=1.77). There was no statistical difference in regards of Rituximab treatment during the study in low and in high IFNα level group, respectively 16% and 38% (p=0.22) at first study visit and 12% and 43% (p=0.07) at second study visit. <h3>Conclusion</h3> The first analysis of Estonian SLE patients' IFNα levels and disease activity shows that measuring IFNα levels can give additional information in some SLE patients in the light of new treatments targeting IFNα, although the general correlation with disease activity and available treatment so far is low. Further studies are in progress to evaluate IFNα levels in larger Estonian SLE population to better understand possible pathogenetic mechanisms in different SLE subpopulations. <h3>REFERENCES:</h3> NIL. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.